Presence and absence of significant twinning: Effects on cold deformed microstructures of single phase Zircaloy 2

Sahoo, Santosh Kumar; Hiwarkar, Vijay; Majumdar, Amit; Samajdar, I.; Pant, Prita; Dey, G.K.; Srivastav, D.; Tiwari, Ratnesh; Banerjee, Suparna

doi:10.1016/j.msea.2009.05.025

Cited by 20 publications

(12 citation statements)

References 34 publications

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“…Dislocation density of samples was calculated using the Variance method, [9,10] which is available for the calculation of dislocation density in hcp-structured materials, e.g. Zr, [11,12] from the 4th-order restricted moments of the individual XRD peak after correcting the instrumental broadening. The calculation error of dislocation density was <5%, and thus yields an error bar.…”

mentioning

confidence: 99%

Extraordinary Toughening by Cryorolling in Zr

Shi

Guo

et al. 2013

Adv Eng Mater

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High strength and good ductility are essential for the applications of structural materials. However, the strength and ductility of materials are often mutually exclusive. For example, deformed materials always exhibit a hardening behavior, i.e. enhanced strength accompanied with reduced ductility. [1] This is attributed to the mutual entanglement and blockage of high-density dislocations induced by plastic deformation, which greatly inhibit the motion of dislocations. [2] Thermal annealing is indispensable for enhancing the ductility of deformed materials at the expense of their strength.Recently, studies show that dislocations in some special configurations are movable, which prevents localized shear deformation and contributes to the ductility of deformed materials. [3] To tailor dislocation configurations in deformed materials, high-density dislocations induced by plastic deformation are indispensable. This can be achieved by suppressing the dynamical recovery of deformed materials using cryogenic deformation that has been successfully employed to study lowtemperature properties of materials, [4] tailor their microstructures and mechanical properties. [5,6] More recently, our studies demonstrate strain rate has a significant effect on the dislocation configurations of cryorolled Zr, and the dislocations in lamella configurations are movable under high stress and contribute to plastic deformation. [7] Moreover, dislocation dynamics simulations show that in hcp Zr no dislocation junction forms between intersecting screw dislocations at low temperature, which results in a weak forest hardening. [8] These studies hint a work toughening behavior, not hardening behavior, may be observed in the hcp Zr if appropriate dislocation configurations, in which dislocations are moveable under high stress, are yielded through cryogenic deformation. To unambiguously confirm this supposition through experimentally procedure, both room temperature (RT) and cryogenic deformation experiments of metal Zr with increased strain were designed and performed in this study, and an extraordinary work toughening behavior is observed in the cryogenically deformed Zr, in contrast to the work hardening behavior of RT-cryorolled Zr. ExperimentalHigh-purity Zr (99.95%) sheets with a fully recrystallized microstructure (average grain size $30 mm) were rolled at RT and liquid nitrogen (LN) temperature at a strain rate of 2.63 s À1 with various strains e ¼ 0.5-2.95, respectively. The cryorolling was performed by immersing the samples into liquid nitrogen for 10 min before and after each rolling pass. The rolling temperature was determined to be À90 to À160°C by using both a Pt100 resistance thermometer and an adiabatic calorimeter. Cryorolled Zr sheets were annealed from 100 to 150°C for 1 h, and the annealed specimens were air-cooled to RT after annealing. The microstructure of cryorolled Zr in the RD-TD plane was characterized using a transmission electron microscope (TEM) and an X-ray diffractometer (XRD) with Cu Ka radiation. Dislocation densi...

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confidence: 99%

Extraordinary Toughening by Cryorolling in Zr

Shi

Guo

et al. 2013

Adv Eng Mater

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“…The latter is expected. Past study [21] also showed that suppression of twinning and more crystallographic slip leads to stronger misorientation developments. The observations in Figures 5(d) and (e) are, however, new.…”

Section: A Experimentalmentioning

confidence: 88%

“…Akhtar and Teghtsoonian [20] showed that alloying elements influence the shape of the hardening curve of single crystals. Reduced grain size has been shown to inhibit deformation twinning, [21][22][23] and grain boundary character has been shown to be important in determining the ease of twin nucleation. [24] Crystallographic texture influences the resolved shear stresses on slip and twinning systems and thus influences the extent of deformation twinning significantly.…”

Section: Introductionmentioning

confidence: 99%

“…[24] Crystallographic texture influences the resolved shear stresses on slip and twinning systems and thus influences the extent of deformation twinning significantly. [3,5,20,21,23,[25][26][27][28][29] The critical resolved shear stress of deformation twinning systems increases less rapidly with decreasing temperature than that of slip systems. Consequently, more deformation twinning occurs at lower temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Deformation Twinning in Zirconium: Direct Experimental Observations and Polycrystal Plasticity Predictions

Singh

Mahesh

Kumar

et al. 2015

Metall Mater Trans A

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Deformation twinning was directly observed in three commercial zirconium alloy samples during split channel die plane-strain compression. One pair of samples had similar starting texture but different grain size distributions, while another pair had similar grain size distribution but different starting textures. Extension twinning was found to be more sensitive to the starting texture than to the grain size distribution. Also, regions of intense deformation near grain boundaries were observed. A hierarchical binary tree-based polycrystal plasticity model, implementing the Chin-Hosford-Mendorf twinning criterion, captured the experimentally observed twinning grains' lattice orientation distribution, and the twin volume fraction evolution, provided the critical resolved shear stress for extension twinning, s 0 ; was assumed much larger than any of the values reported in the literature, based on the viscoplastic self-consistent model. A comparison of the models suggests that s 0 obtained using the present model and the viscoplastic self-consistent models physically correspond to the critical stress required for twin nucleation, and twin growth, respectively.

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“…For comparison, it was considered necessary to evaluate PAS response of the present sample with that of a sample of exact chemistry and grain size but undergoing insignificant twinning. This was achievable easily, as a sample with predominantly (0 0 0 2) starting texture [41] does not have much of visible 4 twins. Necessary specimens were machined and compression tested.…”

Section: Uniaxial Cold Compressionmentioning

confidence: 99%